<!DOCTYPE html>
<html>
<head>
    <style>
        .box{
            height: 0;
            width: 0;
            border: 20px solid transparent;
            border-right-color: rgb(47, 233, 102);
        }
        .jd{
            position: relative;
            background-color: tomato;
            width: 150px;
            height: 100px;
            margin: 100px auto;
        }
        .trangle{
            position: absolute;
            top: -29px;
            right: 15px;
            height: 0;
            width: 0;
            line-height: 0;
            font-size: 0;
            border: 15px solid transparent;
            border-bottom-color: tomato;
        }
    </style>
</head>
<body>
    <div class="box"></div>
    <div class="jd">
        <div class="trangle"></div>
    </div>
</body>
</html>